Process for purifying anthracene press cake



Patented May 29, 1923.

r Fete HARRY D. GIBBS, OF SAN FRANCISCO, CALIFORNIA, DEDICATED, BY MESNEASSIGN- MENTS, TO THE PEOPLE OF THE UNITED STATES.

PROCESS FOR PURIFYING ANTHRACE'NE PRESS CAKE.

Ho Drawing.

Application flled February 8, 1919. Serial No. 275,904.

(FILED UNDER THE ACT OF MARCH 3, 1883, 22 STAT. I, 825.)

To all whom it may concern:

Be it known that I, HARRY D. GIBBS, a citizen of the Unitecll States ofAmerica and an employee of .the Department of Agriculture, residing inthe city of San Francisco, county of San Francisco, State of California,have invented a new and useful Process for Purifying Anthracene PressCake. This application is made under the act of March 3, 1883, chapter143 (22 Stat. 625), and the invention herein described and! claimed maybe used by the Government of the United States or any of its oflicers oremployees in the prosecution of work for the Government or any person inthe United States, without payment to me of any royalty thereon.

The object of my invention is to purify 0 anthracene, carbazole,phenanthrene and other useful compounds found in anthra cene press cakeand separate them from each other in a higher degree of purity and; thusrender these valuable compounds available in a sufiicient degree ofpurity for treatment in various chemical ways .to produce intermediatecompounds and dyes from them.

The process of purifying anthracene, carbazole and phenanthrene hasheretofore been carried out by means of solvents that dissolve one ormore of the constituents more or less completely, thus enabling theseparation by solution and! fractional crystallization. The process isslow, cumbersome and entails a considerable loss of valuable solvents.My process requires no solvents, is inexpensively operated and producesthe desired substances in a higher state of purity.

In describing my process I shall, as an example, describe the severalsteps of the complete process, it being understood that while all of thesteps are not independently novel they have not been heretofore employedin connection with the novel steps of the rocess, for which reason theyhave not satisfactorily accomplished the results attained in thepractice of my invention.

It is well known that the constituents of For- Melting mula.

Boiling point.

Compound. p 01m Acenaphthene Phenanthrene. Acridine CuHln cHHlo CiaHnNCLSHIO CmHpN is lz 200 CisHi:

280 Above 360 {Above 360 Fluoranthrene 217 at 30 mm. pres. Fluorene 295Pseudophenanthrene Above 360 Pyrene Above 360 213", also 360, alsoAnthracene given as 351 Carbazole Methylanthracene 3 Above 360 sens #48the least volatile will separate out first. It

is also true that some of these constituents separate out in so fine astate of division that they are carried suspended in the air for alonger time than those constituents that are denser. This is well known.

I have discovered that when a current of air so charged with thesubstances is caused to move through small orifices the least volatileconstituents separate and aggregate on the edges or against theorifices. Crystallization and separation from the vapor phase is thusassisted by theorifices and the passage of the gas through the orifices.These orifices may be arranged in large numbers in approximately thesame plane in a sheet, plate or screen composed of metal, fiber or othersubstance, or the aggregation of orifices may be attained by use ofgauze,

BI'S.

screen, cloth made of wire, or woven or spun anthracene press cake havelndividual meltfib .in warped or bent surfaces.

I have also found a multiple arrangement of these planes of orifices onthe plan of connecting rooms or compartments offer the additionaladvantage of forming a temperature gradient varying from the highesttemperature where the gas stream enters to the lowest temperature in thefarthestcompartment, the fall in the temperature of the gases beingquite sharp as they pass through the orifices or just after passingthrough the orifices. This temperature gradient between the compartmentsis caused by the removal of heat from the gases as they pass through theorifices by conduction and radiation.

1 do not wish to confine myself to the use of these orifices or screensin multiple in the same plane, but these orifices may be arranged incircles, in spheres, concentric or otherwise, or any figure ofrevolution or I have found that in various cases one arrangementpossesses an advantage over other arrangements depending upon thecharacter and state of the material which is being separated and alsodepending on the size and capacity desired in the apparatus.

I do not wish to confine myself to the use of atmospheric air for thereason that in some cases it is advisable to use furnace gases, fluegases, carbon dioxide or other gases.

The separation of carbazole may be facilitated, if desired, by takingadvantage of the fact the carbazole is an amino acid and unites withmetals to form salts. Very strong caustic soda or potash (sodiumhydroxide or potassium hydroxide), or metallic sodium may be added tothe press cake and melted with it. The sodium or potassium salt ofcarbazole is thus formed and this is not volatilized in the current ofheated air. Since a compound of this nature is hydrolyzed by water givencaustic alkali and carba-zole the air should be dried and everyprecaution taken to keep the amount of moisture present in the melt potat a minimum. The salt of carbazole in the melt may be purified invarious ways, preferably by neutralization with acid and subliming thecarbazole.

An example of the working of this process with the use of alkali isgiven in the following figures compiled from a factory run and this maybe regarded as embodying the essentials of the preferred procedure.However, I do not wish to be confined to this procedure for in verylarge scale operations various modifications will be necessary.

Anthracene press cake was mixed with 5 per cent caustic soda and heatedin a closed iron vesel to 475 F. and a current of air run over it at therate of 3 cubic feet fper minute for each square foot of screen sur aceseparating the first compartment of the condenser from the secon The aircurrent was conducted into the first compartment of the condensingapparatus consisting of a series of compartments separated from eachother by screen made of wire cloth of about one-half inch mesh. Thetemperature of the gas stream entering the first compartment was about200 C. and the temperature of this compartment should be maintainedabove 150 C., and preferably so high as 200 0., and in some cases to 250C.

In large scale operations I consider it an advantage to'dispense withthe use of alkali mixed with the press cake and feed the press cakemolten into the moving air current where it may be distributed by meansof bafiie plates.

The analysis of the anthracene press cake showed approximately 20 percent anthracene, 25 per cent carbazole, 20 per cent oil and moisture,and the remainder the other constituents usually. present, principallyphenanthrene.

The condensed material was collected from the various rooms andanalyzed. The first and hottest compartment showed 43 per centanthracene and 18 per cent carbazole, the middle compartments 25 percent anthracene and 12 per cent carbazole, and the last or coolestcompartment approximately 12 per cent anthracene, 8 per cent carbazole,and the remainder of the 100 per cent mostly phenanthrene.

A second treatment of the material from the first or hottest compartmentwithout using caustic alkali to hold back the carbazole from sublimingfrom the melting pot gave:

First compartment-carbazole 80 to 83%.

Second compartment-anthracene 75%.

Third compartment-almost all phenanthrene.

A third or a fourth treatment of the various fractions is advisable whenfurther purification of the material 'is desired.

The quantities of material purified in a given time depend upon the sizeand arrangement of the apparatus, the volume of the air employed, andthe character of the material.

The air current may be charged with the volatile constituents in variousways, other than described above, for example, by feeding the solid ormolten material into the air stream or passing the air stream over orthrough bafiles containing the material to be volatilized.

The material collecting on the screen or around the orifices may beremoved by shaking or jarring the screens, or by scrapers or brushes,operated by hand intermittently or continuously by mechanical devices.

The material falling from the screens and condensing in the variouscompartments may be removed from time to time by means of chutes in thebottom of the compartment or it may be scraped from the floor of thecompartments and removed through doors placed in the side or bottomwalls.

Having now fully described my invention, whatI claim and desire toprotect by Letters Patent is 1. The process of purifying carbazole,anthracene and phenanthrene by fractional condensation from a moving gasstream, collecting these and other substances in compartments separatedfrom each other by partitions containing a multiplicity of orifices ofsuch size as not to act as a dust catcher. I

2. The process of purifying carbazole, anthracene and phenanthrene byfractional condensation from a moving gas stream, collecting these andother substances in compartments separated from each other by partitionscomposed of cloth with orifices of such size as to permit dust to passthere through freely.

3. A process of treating anthracene presscake, which comprises heatingthe same with an alkali to convert the carbazol present into a salt,then heating further to a temperature suflicient to fractionally sublimeanthracene and other materials, and collecting such sublimed materials.

4. In the fractionation of crude anthracene press-cake, the steps oftreating with an alkali, and thereafter heating to about 200 C. incontact with a flowing gas current, whereby substances other thancarbazol are vaporized, and carried along by said gas current, andthereafter gradually cooling said gas current whereby such vaporizedsubstances are deposited in the solid state.

5. The improvement in the recovery of methyl anthracene, phenanthreneand anthracene, which comprises heating to about 200 C. in a flowing gascurrent, a mixture comprising such materials, and gradually cooling thesaid gas current.

In testimony whereof, I aflix my signature in the presence of twosubscribing witnesses.

HARRY D. GIBBS.

Witnesses:

COURTNEY CoNovER, L. A. SKINNER.

